In the related art, there is a known technology with which figure numbers and version numbers of a ladder program in a numerical control device at a remote location are acquired via a network and managed in a centralized manner (for example, see Japanese Unexamined Patent Application, Publication No. Hei 6-110540).
In addition, in the related art, there is a known technology for managing a ladder-program history (for example, see Japanese Unexamined Patent Application, Publication No. 2006-330867).